Adverse effects due to high level of magnesium ion include flushing, sweating, hypotension, muscular weakness, sedation and confusion. As the blood level begins to exceed 4 mEq/L, deep tendon reflexes are decreased which may be absent at 10 mEq/L. At 12 to 15 mEq/L, respiratory paralysis is a potential hazard.
Treatment of Adverse Effects: An injectable solution of calcium salt (i.e. as gluconate) should always be available for use as antidote. Calcium salt injection should be administered intravenously at a dose of up to 10 mEq to counteract respiratory depression or heart block. If renal function is normal, adequate fluid should be given to assist removal of magnesium from the body. Dialysis may be necessary in patients with renal impairment or severe hypermagnesemia.